Vannin' Home Forums Thread Like Summary - Exhaust Manifold Heat Riser - Direction?

Hi everyone, on our 1985 Dodge B350 with the 360 5.9l V8 there is this exhaust manifold heat riser on the driver's side. Basically a wheel/valve with a thermostat coil spring, and on it's other side a tension spring.
The thermostat spring's hook that holds onto the rod has broken off, and sometimes I can hear that internal flapper rattling, so my questions are:

- With the engine cold/off, which side would that wheel/valve turn normally be, towards the clockwise (passenger) or counterclockwise (driver) side? That is, once the engine is warm and running, should that wheel/valve be turned towards the right/passenger side (clockwise)?
- As the thermostat spring is not longer usuable, should I just turn that wheel/valve clockwise (towards the right/passenger side) or counterclockwise, and just leave it there to avoid an overcooking of the manifold, carb, etc.?

In the future I will have it drilled out and holse tapped close, or just try to replace that damn coil spring, but until then I need to turn it to the right direction...

The heat riser butterfly valve inside the exhaust manifold should be in the closed position when the engine is cold, and once the engine has warmed up, it should be fully open.

What it does is create backpressure during warmup to force hot exhaust gas through a passage in the intake manifold, underneath the carburetor, to the driver side exhaust manifold, for the heat to assist with vaporization of the fuel droplets from the carb. Without this heat, the fuel droplets can pool on the cool metal base of the intake manifold passage.

I have to wonder if the rattle you hear might actually be due to a missing or weak part... you did mention seeing a tension spring, but how rusty is it? Springs weaken a lot with surprisingly little rust. On the opposite side of the valve shaft from the coil spring, there is supposed to be a small tension spring whose one end loops over the valve shaft, and the other end loops over the little stud welded onto the manifold. This springs purpose in life is specifically to dampen rattling of the valve shaft. It isn't a very strong spring; it's just used as a damper, to hold the valve shaft down against its pivot. Perhaps if you retension or replace this spring the rattle will stop. That won't prevent the butterfly valve from finding random locations though.


I might suggest that you bend another hook onto the end of the coil spring if you can. It only requires sufficient force to get the valve open and closed. It's a very useful cold drivability feature.